Back relaxation effect

K, there is evidence for a small relaxation effect which can be interpreted as a flow back of molten polystyrene into the initially created mark. 

Mobility is also reduced slightly by another phenomenon termed the relaxation effect. Here the charged species, as it is displaced by the electric field from the center of the double layer, is acted on by the opposite charge of the double layer to pull it back [38]. 

Tension in muscles at the back of the neck is thought to be a contributory factor to tension headache. Sedating antihistamines are included in some products for their claimed muscle-relaxant effect. 

Chapter 2 is focused on physical principles of IPMCs. It starts with an introduction to the fundamentals of IPMCs, including the fabrication techniques, and then takes a careful look at the effect of electrodes on material behavior and actuation performance. Several novel approaches, including a fluorescence spectroscopic visualization method, are then used to yield unique insight into IPMC actuation behaviors, such as the back-relaxation phenomenon. More sophisticated configurations than a singlelayer bender are also discussed in this chapter. 

FIGURE 4.6. (a) Back-flow effect during the process of the director reorientation, (b) The dependences of the velocity V and director angle 0 on the coordinate z are given at different times ti < t2 < ta- The dotted line shows possible nonmonotonous relaxation of 0 at high voltages ti < ti < t2 < ta-... 

The evolution of the piston displacement upon compressing the LDA sample is shown in Figure 5. For comparison, the results obtained upon PIA of ice Ih are included. The LDA-to-HDA transformation occurs at f 0.6 GPa, as indicated by the sudden change in d(/. This pressure is lower than the pressure at which ice Ih transforms to HDA ( 1 GPa). Still, the LDA-to-HDA transition is at least as sharp as the ice Ih-to-HDA transition and, thus, it also resembles a first-order transition in its volume change. We note that the density of HDA at 1 bar and T — 77K is, within error bars, the same density of the HDA samples obtained from PIA of ice Ih, 1.17 g cm . Moreover, the X ray diffraction patterns of HDA, obtained from ice Ih and LDA, are also very similar to each other [62]. Therefore, the HDA form obtained from LDA is apparently the same amorphous ice that results from PIA of Ih at r = 77K [24,62]. If the LDA to HDA transformation is indeed a true first-order transition, then one would expect to observe that HDA transforms back to LDA upon decompression. Otherwise, the LDA to HDA transformation could be interpreted as a simple relaxation effect of LDA. In this case, there would be a single amorphous phase of water (LDA), and HDA, instead of being a new amorphous phase different from LDA, would be a relaxed version of LDA [63]. Figure 5 shows... 

If the laser pulse applied to the sample molecules is sufficiently long and intense, a molecule (represented by a two-level system) will be driven back and forth between the two levels at the Rabi flopping frequency (2.134). The time-dependent probability amplitudes a (t) and a (t) are now periodic functions of time and we have the situation depicted in Fig.2.30. Since the laser beam is alternatively absorbed (induced absorption E ) and amplified (induced emission E2-> E ), the intensity of the transmitted beam will display an oscillation. Because of relaxation effects this oscillation is damped and the transmitted intensity reaches a steady state determined by the ratio of induced to relaxation transitions. According to (2.133) the Rabi frequency depends on the laser intensity and on the detuning molecular eigenfrequency o) 2 laser frequency co. This detuning can... 

A. Yelon Yes. When we have the sample on the glass, we heat it up to above Tn and the birefringence goes away and when we bring it back down to room temperature it s not there anymore. So, no, it does not come back. That means that either it wasn t the stable state in the first place or that in cooling it down, the relaxation effects are such that it doesn t get back to what would be the equilibrium condition. 

In summary, all the experiments expressly selected to check the theoretical description provided fairly clear evidence in favour of both the basic electronic model proposed for the BMPC photoisomerization (involving a TICT-like state) and the essential characteristics of the intramolecular S and S, potential surfaces as derived from CS INDO Cl calculations. Now, combining the results of the present investigation with those of previous studies [24,25] we are in a position to fix the following points about the mechanism and dynamics of BMPC excited-state relaxation l)photoexcitation (So-Si)of the stable (trans) form results in the formation of the 3-4 cis planar isomer, as well as recovery of the trans one, through a perpendicular CT-like S] minimum of intramolecular origin, 2) a small intramolecular barrier (1.-1.2 kcal mol ) is interposed between the secondary trans and the absolute perp minima, 3) the thermal back 3-4 cis trans isomerization requires travelling over a substantial intramolecular barrier (=18 kcal moM) at the perp conformation, 4) solvent polarity effects come into play primarily around the perp conformation, due to localization of the... 

A comparison with Burchard s first cumulant calculations shows qualitative agreement, in particular with respect to the position of the minimum. Quantitatively, however, important differences are obvious. Both the sharpness as well as the amplitude of the phenomenon are underestimated. These deviations may originate from an overestimation of the hydrodynamic interaction between segments. Since a star of high f internally compromises a semi-dilute solution, the back-flow field of solvent molecules will be partly screened [40,117]. Thus, the effects of hydrodynamic interaction, which in general eases the renormalization effects owing to S(Q) [152], are expected to be weaker than assumed in the cumulant calculations and thus the minimum should be more pronounced than calculated. Furthermore, since for Gaussian chains the relaxation rate decreases... 

---